Memory replay refers to the process during sleep wherein brain activity representing previously learned experiences is reactivated in order to consolidate such activity into long-term memory. Conventional memory enhancement techniques that target the mechanism of memory replay have been studied in an academic context. One convention technique (Ken Paller of Northwestern University) has shown that playing sounds randomly during sleep can improve memory on simple tasks. This approach is known as targeted memory reactivation (TMR).
Other conventional techniques (Jan Born) have applied direct current neurostimulation in an open-loop fashion (e.g., not dependent on ongoing processes in the brain to improve the specificity of timing). Another technique (Flavio Frohlich) has targeted a different biomarker known as the sleep spindle using alternating current stimulation in a closed-loop system.
A challenge of using these conventional memory enhancement interventions is the inability to fully improve memory retention by targeting specific neurophysiological events that occur during sleep. These events may occur only at specific stages of sleep (e.g. deep sleep, REM sleep) and even more precisely only over short intervals (e.g. 500 ms). Conventional memory enhancement techniques do not provide real-time detection and delivery that enables precise targeting to biological phenomena as they occur. Furthermore, conventional memory enhancement techniques do not necessarily use targeted neurostimulation to locations demonstrated to be memory-type specific. It is therefore desirable to provide an apparatus, system, and method for applying memory enhancing interventions (e.g. sensory stimulation, direct current neurostimulation) based on the real-time detection of relevant biomarkers and which can also simultaneously titrate the delivery of these interventions based on real-time assessment of neurophysiological feedback in a closed-loop.